Conventional fire hydrants offer access to a municipal water supply in a manner in which operatives with ill intent may appreciate. Briefly, conventional fire hydrants include at least one nozzle for coupling to a fire hose. A threaded cap closes off the nozzle when the hydrant is not in use. The hydrant also includes a hydrant valve which controls flow of water from the water supply through the hydrant, through the nozzle, and into the fire hose.
Conventionally, the barrel of the hydrant between the nozzle and the hydrant valve, which is in the lower portion of the hydrant, accommodates several gallons of fluid or solids. Accordingly, it is possible to unscrew a nozzle cap, introduce gallons of toxin, reattach the nozzle cap, and open the hydrant valve to allow the toxins to communicate with and flow, by gravity and perhaps at least to some extent by Bernoulli's principle, into the municipal water supply, since water pressure from the water supply can not force the toxins back out of the hydrant because the nozzle cap is attached.
An example of a system and method for preventing toxins from being introduced to a water supply through a hydrant is described in U.S. Pat. No. 6,868,860, entitled “Fire Hydrant With Second Valve,” the entire contents of which are hereby incorporated by this reference. In some examples described in U.S. Pat. No. 6,868,860, a valve structure is introduced between the nozzle and the primary valve that makes it more difficult or impossible to introduce toxins into a water supply through a fire hydrant. The valve structure prevents or substantially prevents the flow of water through the hydrant upon certain conditions and closes off portions of the hydrant barrel when a nozzle is open but the hydrant valve is closed. Generally, the valve structure can include a seat, a restriction member, and a biasing structure.
Retrofitting fire hydrants with secondary valves may be accomplished by removing the hydrant barrel, inserting the secondary valve and affixing the seat to the hydrant body with an adhesive or mechanical means, such as a screw. While this is an effective method for installing the secondary valve, another method is needed to retrofit a fire hydrant with the secondary valve. For example, retrofitting hydrants that include an off-centered actuator rod or a different shaped barrel, such as triangular or cone can be relatively difficult and, in some cases, impossible.